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Gutter bugs

SURFERS and swimmers are used to worrying about sewage outflows. Now they
have a new concern—it seems that water flowing into the sea from the
drains of city streets can also make you ill.

In older American cities, and in countries such as Britain, drains on streets
empty into the sewer system. But in Los Angeles and many other cities, rainfall
is channelled through separate storm drains. Even during summer, says Robert
Haile of the University of Southern California in Los Angeles, the city’s storm
drains pour up to 100 million litres of water a day into Santa Monica Bay.

Haile and his colleagues interviewed 13 278 visitors to beaches in summer
1995. They analysed water samples for potentially pathogenic bacteria and
viruses, and asked swimmers whether they suffered any adverse symptoms.

Bacteria and viruses were abundant near the drain outfalls, their numbers
reducing gradually with distance. People who swam near the outfalls were 50 per
cent more likely to suffer symptoms including fever, chills, ear discharge and
coughing with phlegm (Epidemiology, vol 10, p 355). But farther than
about 50 metres away from the outfalls, swimmers seemed to suffer no ill
effects.